A recent improvement in ferroelectric capacitor memory devices uses manipulation of the dielectric properties as opposed to the polarization to effect the memory function. Those devices, explained more fully in a copending U.S. patent application, "Ferroelectric Space Charge Capacitor Memory", Ciaran J. Brennan, filed on even date herewith and incorporated herein by reference, manipulates the space charge to store and non-destructively read out the stored data. The ferroelectric space charge memory devices are typically fabricated using thin film monolithic integrated circuit technology. Such devices are subject to uneven film thicknesses and other manufacturing variations. This can result in a lack of uniformity in the capacitive values or other dielectric properties over the area of the chip. Thus when a plurality of such devices are to be written to and read from as a group, some of them may never reach or always exceed uniform levels representing the logical states of stored data: a memory device may always read a "1" or "0" regardless of the value actually written into it.
Further, even if the group or assembly of ferroelectric space charge capacitor memory devices is actually operating within the proper range, the change or drift with time and/or temperature may well shift one or more such devices into an operation region where they are no longer responding accurately.